I've just been introduced to this cool piece of software, that generates procedural cities. This is a standalone software that can use sateline photos, data from openStreetMap.org, or using custom maps for a custom designed city, to generate geometry and textures for use. It can import export standard geometry formats like DXF, OBJ and VUE files. It can even export textures and multiple UV sets, including the generation of RIB files for Renderman compliant renderers.
After the city is generated, the user can go and interactively change the individual buildings or add roads and features to further refine the look. Slopes and curved roads are supported. Building parameters include height, width, number of storeys, number of windows, the age (constructed in which year), and many more!
Check out the example videos here!